It's easy to confuse diffusers and humidifiers. They look similar, both produce a fine mist, and they can even overlap in certain functions. But these two devices serve quite different purposes—and understanding the distinction helps you choose the right one for your home.
The short answer? A diffuser disperses essential oils into the air for aromatherapy benefits, while a humidifier adds moisture to combat dry air. One is about scent and therapeutic effects; the other is about humidity levels.
Let's break down exactly how they differ, what each does best, and whether you might actually need both.
What Is a Diffuser?
A diffuser's primary job is to break down essential oils into tiny particles and disperse them throughout a room. The goal is aromatherapy—filling your space with scent and allowing you to breathe in the beneficial compounds found in essential oils.
We work with oil diffusers daily in our Wellington studio, and the thing that surprises most customers is how little water they actually use. Most ultrasonic diffusers hold just 100–300ml, and you only need a few drops of essential oil per session. The mist they produce is incredibly fine—more of a fragrant vapour than actual moisture.
Types of Diffusers
Ultrasonic diffusers are the most popular choice for home use. They use high-frequency vibrations to break water and essential oils into a cool mist. They're quiet, safe (no heat involved), and double as a subtle night light in many designs.
Nebulising diffusers work without water entirely. They use pressurised air to atomise pure essential oil, delivering a more concentrated scent. These are brilliant for larger spaces but use oils faster.
Reed diffusers take a completely different approach—wooden reeds absorb fragrance oil from a bottle and release scent passively. No power required, no mist produced, just gentle continuous fragrance.
Heat and evaporative diffusers use warmth or a small fan to disperse scent. They're simple and affordable, though heating can reduce the potency of some essential oils.
What Is a Humidifier?
A humidifier's purpose is straightforward: increase the moisture content in your air. This is particularly useful during winter when heating systems dry out indoor air, or if you live in a naturally dry climate.
Experts recommend keeping indoor humidity between 30% and 50%. Below 30%, you'll likely notice dry skin, irritated nasal passages, static electricity in your hair and clothes, and even cracking wooden furniture. A humidifier addresses all of these by releasing water vapour into your environment.
Types of Humidifiers
Ultrasonic humidifiers work similarly to ultrasonic diffusers but with much larger water tanks (often 2–6 litres) designed for sustained output. They're quiet and energy-efficient.
Evaporative humidifiers use a wick filter and fan to naturally evaporate water into the air. They're self-regulating—as humidity rises, evaporation naturally slows.
Warm mist humidifiers (also called steam vaporisers) boil water to create steam. The heat kills bacteria before release, but they use more energy and aren't ideal around children due to the hot water.
Impeller humidifiers use rotating discs to fling water through a diffuser, creating a cool mist. They're affordable and safe for kids' rooms.
Key Differences at a Glance
| Feature | Diffuser | Humidifier |
|---|---|---|
| Primary purpose | Disperse essential oils for scent and aromatherapy | Add moisture to dry air |
| Water tank size | Small (100–500ml typically) | Large (2–6+ litres) |
| Coverage area | Single room | Single room to whole house |
| Uses essential oils | Yes—this is the point | Not recommended (can damage the unit) |
| Adds significant humidity | Minimal | Yes—this is the point |
| Maintenance | Light cleaning weekly | Regular cleaning essential to prevent bacteria and mould |
Health and Comfort Benefits
Benefits of Using a Diffuser
Diffusers let you harness the therapeutic properties of essential oils. Eucalyptus oil can help clear congestion during cold season. Lavender may promote relaxation before bed. Peppermint can boost focus and energy. The diffuser simply delivers these benefits throughout your room rather than requiring direct application.
Beyond aromatherapy, many people find the gentle mist and soft light of an ultrasonic diffuser creates a calming ambiance—particularly in the evening.
Benefits of Using a Humidifier
Proper humidity levels (that 30–50% sweet spot) can ease breathing, reduce snoring, prevent dry skin and chapped lips, protect wooden furniture from cracking, and may even help reduce the survival of airborne viruses. If you wake up with a dry throat or notice your skin feels tight in winter, low humidity is likely the culprit.
Can You Use Essential Oils in a Humidifier?
This is one of the most common questions we get, and the answer is generally no—unless your humidifier specifically states it's designed for oils.
Here's why: essential oils can degrade plastic components and clog the mechanisms in standard humidifiers. They may also void your warranty. Humidifiers are engineered for water only, with larger tanks and different internal parts than diffusers.
If you want both humidity and aromatherapy, your best options are to run the devices separately, or look for a hybrid unit specifically designed for both functions.
Maintenance Considerations
Both devices require regular cleaning, but humidifiers demand more attention due to their larger water reservoirs.
Diffuser maintenance is relatively simple: empty unused water after each session, wipe the basin weekly, and do a deeper clean with diluted white vinegar monthly. Because diffusers use small amounts of water, there's less opportunity for bacteria or mould to develop.
Humidifier maintenance is more involved. The larger tank should be emptied and dried daily when in use. Weekly deep cleaning is essential—standing water in a warm environment is a perfect breeding ground for bacteria and mould, which then get dispersed into your air. Some humidifiers also have filters that need regular replacement.
Which One Do You Need?
Choose a diffuser if:
- You want to enjoy essential oil aromatherapy
- Your primary goal is scent and ambiance
- You don't have significant dry air issues
- You want a low-maintenance option
Choose a humidifier if:
- You experience dry skin, dry throat, or respiratory irritation
- Your home has low humidity (especially in winter)
- You want to protect wooden furniture and instruments
- You need whole-room or whole-house moisture control
Consider both if:
- You want aromatherapy benefits AND live in a dry climate
- You're using a diffuser but still noticing dry air symptoms
- You want targeted scent in one area and humidity throughout
For most New Zealand homes—particularly in places like Wellington where we're no strangers to damp—a diffuser is often all you need. But if you run heat pumps through winter and notice the air drying out, adding a humidifier to your setup can make a real difference to comfort.
Ready to Find Your Perfect Diffuser?
If you're after aromatherapy and beautiful scent throughout your home, explore our range of ultrasonic oil diffusers. We've tested dozens of models to curate a collection that balances performance, aesthetics, and value—all backed by our NZ-based support.
Pair your diffuser with our pure essential oils or fragrance oils to create the perfect ambiance for any room.